Nordyne G6RC100C-16 Pressure switch problem

[EdZayas]

A few weeks ago my furnace was operating intermittently. I check it and found the pressure switch was causing the problem(three flashes). So I ordered a replacement from your company. It arrived promptly(thanks). Today I decided to replace the switch. After the installation the problem remains, three flashes. I have checked the hoses and they look fine. I put the old pressure switch back and the darn furnace started up. What else can I do to make sure it continues to start up? Thanks in advance for your help. Ed in Chicago.

[Robert]

Hi Ed,

That can be due to the air pipe to booster motor.induced draft motor being clogged/damaged, the motor itself being bad or dirty, motor wheel clogged or dirty, hoses/tubes being loose, clogged, kinked full of water, the pressure switch being bad or intermittant or no 24vac to the switch.

Any of those will cause you to get the 3 flashes as any will keep switch from closing.


The switch itself is most often the cause, but sometimes it is one of the others or a combo of them.

Would need to check water column pressure to know if switch itself is supposed to be closing or not.

Check and be sure you have 24vac to one side of switch at all times during cycle of heat mode.


Thanks,
Robert

[EdZayas]

Hi Robert,

It is happening again! The three flashes are back! Robert, how do I hook up my voltage meter to check for the voltage on the pressure switch? If I remove the cables the furnace won't run. Also how much voltage is there suppose to be at the gas valve? I am getting 15 volts ac. Is this correct? Just in case I ordered a new voltage regulator and hoses. Thanks for the help!

[Robert]

Hi,

You place one meter lead on one pressure switch terminal and the other to a screw or something for ground.

Then do same on other terminal.

Should read 24vac on one side only.

IF it is ok and closes when supposed to, you will then have 24vac to ground on both sides.


Should have 24 to 28vac at gas valve.


Thanks,
Robert

[EdZayas]

Thanks for the info Robert. Everything checked out fine. However I still get intermittent use out of the furnace. This morning I noticed that the circuit board had a burnt spot below the white thermostat wire connection. It appears that a resistor failed. So I ordered a new circuit board. I hope this fixes all the problems. Thanks again for your help.

[Robert]

Hi,

You're very welcome, happy to help. Thanks for update, hopefully that will resolve any issues.



Thanks,
Robert